Test shots for A100 with Cokin filters

[psccy]

Hi guys...

Being a bit daring this few days... bought a Cokin P07 filter and cut it to fit a 77mm (Thanks Ark19!)

This are some test shots done with Sony A100, Tokina AF 20-35mm and Cokin P07. All Shots straight from camera, only resized for easier viewing...

C&Cs please!

#1 ISO400, 20mm, 4 sec, F3.5

Quite bright, but I'm not satisfied that I am shooting at 4 sec.

#2 ISO400, 20mm, 2.5 sec, F3.5

much darker... 2.5 sec... sensing that something is wrong in the middle...

#3 ISO400, 35mm, 3.2 sec, 5.0

flare in the centre... suspected... sianz...

Anyone can suggest how I might still be able to use the lens? (at least till I find a better one...)

[teerex]

#2 look like to have the best exposure to me. Did a quick PP on it, looks ok.

#3 ya there's a flare or is it a hot spot just behind the goal post.

[PandaOng]

your hotspot looks kinda cute.....it is very define

[JeffryZ]

Is the hot spot caused by the lens reflecting onto the back of the filter? Is this a case where covering the optical viewfinder would help? I don't encounter this with my converted camera but notice that most of the people here trying IR are using filters.

This site http://heim.ifi.uio.no/~gisle/photo/ir.html#lenses says it can be caused by lens coatings- so I guess less expensive lenses would work better for infrared?

[psccy]

Originally Posted by JeffryZ Is the hot spot caused by the lens reflecting onto the back of the filter? Is this a case where covering the optical viewfinder would help? I don't encounter this with my converted camera but notice that most of the people here trying IR are using filters. This site http://heim.ifi.uio.no/~gisle/photo/ir.html#lenses says it can be caused by lens coatings- so I guess less expensive lenses would work better for infrared?

Not sure which category I should place my lens in. I think mine has 4 colour coatings?
the hotspot seems to be more pronounced at 35mm... much less for 20mm...

[psccy]

Originally Posted by PandaOng your hotspot looks kinda cute.....it is very define

not too sure why... as said above, may be cos #3 was shot at 35mm (with a 20-35mm)

Will try more again tomorrow.

[psccy]

Originally Posted by teerex #2 look like to have the best exposure to me. Did a quick PP on it, looks ok. #3 ya there's a flare or is it a hot spot just behind the goal post.

Still figuring out my exposure... Will ask more questions the next time we meet up for a shoot. Think I quite like the 20mm shots... nice and wide....

my own verdict thus far...

Sigma 18-50 F2.8
Cosina 28-105 F2.8-3.5 (soft)
Tokina 20-35 3.5-4.5 (got potential)

I also quite like the shots straight out from a Cokin... more colour let in... will try to PP late...
Teerex... what you do to #2... teach me leh...

[SingaConnect]

you took the photo at PJC outside gym? going off topic

[teerex]

Originally Posted by psccy I also quite like the shots straight out from a Cokin... more colour let in... will try to PP late... Teerex... what you do to #2... teach me leh...

Wah, teach you ah? I still learning also leh.

I prefer the first one, with the lighter blue sky.

This one just the usual. Levels, Channel Swap, H/S adjustments, Sharpening.



This one, layer and masked the sky for enhancement of the blue sky.

[psccy]

hmm... must try your second method... but not too sure the steps to take...

[JeffryZ]

Digging a bit further I found an article that says the hot spot can be worse the more a lens is stopped down. But one problem with filtered IR shooting is that you need to stop down to get the longer exposures needed. Maybe shoot wider open with a neutral density filter added? How many elements a lens has and the coatings can also have an effect on the hot spot- fewer is apparently better on both.

[night86mare]

Originally Posted by JeffryZ Digging a bit further I found an article that says the hot spot can be worse the more a lens is stopped down. But one problem with filtered IR shooting is that you need to stop down to get the longer exposures needed. Maybe shoot wider open with a neutral density filter added? How many elements a lens has and the coatings can also have an effect on the hot spot- fewer is apparently better on both.

do you know what you are talking about?

i don't understand why you think that ir needs long exposure for sure, and why you need to stop down to obtain the long exposure

the thing is, dof, most people use ir to take landscape-sque pictures, and if you're shooting a landscape, at say, f/4.0, the depth of field is going to be pathetic, and the picture will look pretty soft overall

[creampuff]

Bro, go easy - new member...
night86mare is correct on the point of the DOF, stopping down to a smaller aperture is going to get better sharpness. Obviously if the lens exhibits hot spots, stopping down will define the hot spot even more. If your camera allow for shorter exposures, it is a boon as it opens up more possibilities.

[psccy]

Originally Posted by JeffryZ Digging a bit further I found an article that says the hot spot can be worse the more a lens is stopped down. But one problem with filtered IR shooting is that you need to stop down to get the longer exposures needed. Maybe shoot wider open with a neutral density filter added? How many elements a lens has and the coatings can also have an effect on the hot spot- fewer is apparently better on both.

Originally Posted by night86mare do you know what you are talking about? i don't understand why you think that ir needs long exposure for sure, and why you need to stop down to obtain the long exposure the thing is, dof, most people use ir to take landscape-sque pictures, and if you're shooting a landscape, at say, f/4.0, the depth of field is going to be pathetic, and the picture will look pretty soft overall

IMHO, I think both of you have valid points...

I think JeffryZ is looking at it from mainly a un-modded camera that has a relative good IR blocker, hence the issue of the longer exposure. At the moment, my A100 is shooting at minimum 2.5 sec at ISO400. At ISO100, I need at least 5sec...

I'm not sure about the use of the neutral density filter... As I have a long exposure time, I don't want to extend it even more by letting less light in... Still I will give it a try... no harm, only waste shutter count

The design of the lens obviously affects the shot. the tokina lens has 4 coatings... and the flare is definitely more apparent when I shoot at 35mm, which suggest to me that the aperture size may affect the flare... when I further test the lens, I will try longer expousre with a small aperture (say F8 perhaps) and see the effect...

night86mare is very right about the DOF... I don't like soft shots... which is the very reason I have tried out many of my lens... looking for a sharper lens for IR. As I mentioned, my cosina 28-105 gives good flare control but generally soft pictures, probably due to its pull push zoom design...

Sigh... anyone used a tamron 11-18mm (same lens as Sony SAL 11-18mm!!) before for IR? its on my wishlist at the moment...

[davidkow]

Originally Posted by psccy Hi guys... Being a bit daring this few days... bought a Cokin P07 filter and cut it to fit a 77mm (Thanks Ark19!) This are some test shots done with Sony A100, Tokina AF 20-35mm and Cokin P07. All Shots straight from camera, only resized for easier viewing... C&Cs please Anyone can suggest how I might still be able to use the lens? (at least till I find a better one...)

hi,cameron, i have this len before,very easy have hotspot,u can refer last time my soto taken at jpg gdn.

[JeffryZ]

Thank you for the additional infomation. I was just trying to understand the possible source of hot spots and how people can try to avoid them. I understand that newer unmodded cameras have stronger IR blocking filters over their sensors and require longer exposures to capture an infrared image. Generally exposure times can be increased by using a higher f/stop or by putting an additional filter like a neutral density filter in front of the lens to reduce the amount of light gettting to the sensor but perhaps the IR filter you use reduces the light enough by itself and you need the longer exposure already because less light is getting through in the first place. My own camera is modified so I do not have to deal with this issue.

[night86mare]

Originally Posted by JeffryZ Thank you for the additional infomation. I was just trying to understand the possible source of hot spots and how people can try to avoid them. I understand that newer unmodded cameras have stronger IR blocking filters over their sensors and require longer exposures to capture an infrared image. Generally exposure times can be increased by using a higher f/stop or by putting an additional filter like a neutral density filter in front of the lens to reduce the amount of light gettting to the sensor but perhaps the IR filter you use reduces the light enough by itself and you need the longer exposure already because less light is getting through in the first place. My own camera is modified so I do not have to deal with this issue.

not sure, but i think there is misconception here

1) ir only requires long exposure timings because of the ir blocking filters, which in addition to the amount of light the r72 filter or whatever you use, increases exposure timing

so there is no actual need to "limit" the light reaching the sensor using high f-stop or nd filter

so while all your statements in the above post are correct, i tend to get the idea that you think that all infrared photos need long exposure timings, which is weird, if i could i would want to cut down the exposure timing, but if i do so i will lose dof, sigh

hot spots has been linked to diffraction (google this) , this is what was mentioned to me by some of the ir regulars in the past. diffraction only comes about when a small aperture is used, so sometimes, when you open up the aperture (and sacrifice dof) the hot spot problem might be resolved, but not necessarily all the time =)